The present application is based on Japanese priority application No.2000-134967 filed on May 8, 2000, the entire contents of which are hereby incorporated by reference.
The present invention generally relates to fabrication of semiconductor devices and more particularly to a thermal processing apparatus and method used in a fabrication process of a semiconductor device.
A single-wafer thermal processing apparatus is an apparatus used for fabricating a semiconductor device on a semiconductor wafer. A single-wafer thermal processing apparatus applies a thermal processing to semiconductor wafers one by one. Particularly, there is a type of single-wafer thermal processing apparatus that uses a lamp as a heat source. The apparatus of this type is important as it is used extensively in various annealing processes, oxidation processes, CVD processes, and the like.
FIGS. 8 and 9 show the construction of a conventional thermal processing apparatus.
Referring to FIGS. 8 and 9, the thermal processing apparatus includes a processing vessel 1 accommodating therein a semiconductor wafer to be processed, wherein the processing vessel 1 includes a laterally elongated gas inlet and a laterally elongated gas outlet on respective, mutually opposing sidewalls with a height of about 15 mm. The processing vessel 1 further includes a support ring 13 at a bottom part thereof for holding the semiconductor wafer, wherein the support ring 13 is provided rotatable and is driven via a magnetic coupling not illustrated in response to an external magnetic energization.
The processing vessel 1 further includes a lamp 14 at the ceiling part as a heat source heating the semiconductor wafer on the support ring 13, and there is provided a cooling water passage 15 in the sidewall of the reaction vessel 1 such that the cooling water passage 15 extends in a circumferential direction of the reaction vessel 1. By causing to flow cooling water through the cooling water passage 15, the sidewall of the reaction vessel 15 is cooled.
In such a single-wafer thermal processing apparatus, there is a requirement that the temperature distribution in the wafer should be uniform during the thermal processing conducted therein, wherein the required degree of temperature uniformity is increasing in recent semiconductor devices formed on a wafer with an increased degree of device miniaturization.
From the viewpoint of the increased degree of uniformity of temperature distribution required for the thermal processing apparatus, the conventional thermal processing apparatus of FIGS. 8 and 9 is not satisfactory as the cooling water experiences a temperature rise as it is caused to flow from the cooling water inlet to the cooling water outlet along the cooling water passage 15. Thus, there can be a case in which the temperature of the cooling water 15 is much higher at the cooling water outlet as compared with the temperature at the cooling water inlet, and there is formed a circumferential temperature distribution profile along the sidewall of the processing chamber 1. In such a case, there appears a temperature difference between the left-half part of the sidewall close to the cooling water inlet and right-half part of the sidewall close to the cooling outlet in the plan view of FIG. 9.
In the processing vessel 1, it should be noted that there is formed a gas flow from one sidewall where the gas inlet 11 is provided to an opposing sidewall where the gas outlet 12 is provided. In an ordinary pressure process in particular, as in the case of conducting an annealing process while supplying an inert gas to the wafer under the ordinary pressure, there appears a velocity distribution in the gas flow supplied from the laterally elongated gas inlet 11 such that the gas velocity is large at the central part and small at the lateral edge part of the sheet-like gas flow.
From above, it will be understood that the conventional thermal processing apparatus has a problem of difficulty in achieving a uniform temperature distribution over the entire surface of the wafer W processed therein. In order to minimize the foregoing problem, the conventional thermal processing apparatus has adopted a rotating mechanism rotating the wafer W with respect to the lamp 14. While such a construction may be effective when the wafer W is rotated at a high speed, rotation of the wafer at a high speed causes a problem such as particle generation. Thus, there is a limitation in such an approach.
Accordingly, it is a general object of the present invention to provide a novel and useful thermal processing apparatus wherein the foregoing problems are eliminated.
Another and more specific object of the present invention is to provide a thermal processing apparatus that realizes a uniform environment with respect to a substrate processed therein in a circumferential direction thereof.
Another object of the present invention is to provide a thermal processing apparatus comprising:
a processing vessel accommodating therein a stage, said stage being adapted for holding a substrate to be processed;
an evacuation system connected to said processing vessel;
a heater disposed so as to heat said substrate on said stage;
a gas inlet port provided on said processing vessel for introducing a gas into said processing vessel; and
a coolant passage provided in a circumferential wall of said processing vessel, said coolant passage comprising: a first part connected to an inlet port of said coolant and extending along said circumferential wall of said processing vessel to a turn-around point, and a second part connected to said turn-around point and extending along said circumferential wall in a reverse direction to said first part to an outlet port of said coolant.
Another object of the present invention is to provide a thermal processing method of a substrate comprising the steps of:
placing a substrate on a stage provided in a processing vessel; and
heating said substrate while supplying a gas in said processing vessel,
said step of heating being conducted while causing to flow a coolant through a circumferential wall of said processing vessel first in a first direction from a coolant inlet port to a turn-around point and then in a second, opposite direction from said turn-around point to a coolant outlet port.
According to the present invention, the temperature profile in the coolant, which may be a cooling water, flowing through the first part of the cooling medium passage is compensated by the temperature profile in the second part, and a highly uniform temperature distribution is achieved in the circumferential wall of the processing chamber. Thereby, a uniform thermal processing becomes possible in the processing chamber. In view of reduced temperature difference caused in the coolant in the second part of the passage, it is desirable to provide the second part in the circumferential wall at a location closer to the substrate.
Another object of the present invention is to provide a thermal processing apparatus, comprising:
a processing vessel accommodating therein a stage, said stage being adapted for holding a substrate to be processed;
an evacuation system evacuating to said processing chamber;
a heater disposed so as to heat said substrate on said stage;
said processing vessel having an opening and a depression in a circumferential wall thereof such that said opening and said depression oppose with each other with respect to a central axis of said processing vessel, said opening being connected to a gate valve;
said processing vessel further having a gas inlet port and an evacuation port on said circumferential wall such that said gas inlet and said evacuation port oppose with each other with respect to said central axis of said processing vessel, said evacuation system being connected to said evacuation port,
said gas inlet port being located at an angular position offset from said opening by 90xc2x0 with respect to a central axis of said processing chamber.
According to the present invention, a uniform distribution is achieved for the thermal radiation and thermal conduction from the vessel circumferential wall to the substrate along the circumferential direction of the processing vessel. Thus, a highly uniform temperature distribution is achieved in the substrate during the thermal processing process conducted in the processing vessel.
It is preferable to provide an observation window in the depression. Further, it is preferable to provide the gas inlet in the form of laterally elongated slit having a height of 0.5-2 mm. By doing so, uniform supplying of the processing gas to the substrate becomes possible.
Other objects and further features of the present invention will become apparent from the following detailed description when read in conjunction with the attached drawings.